The invention relates to an atomic beam resonator, particularly with cesium-beam, advantageously to produce a reference frequency for the frequency stabilization of a quartz oscillator, and comprising, arranged in series in the direction of the beam, an atomic beam source, a first state selector, an interrogating area including a waveguide body constituting a Ramsey-type two arms resonant cavity, the arms of which are transversally traversed by the atomic beam, a second state selector, a photon sensor device for producing the useful output signal of the resonator and a device for injecting into the resonant cavity an interrogating signal produced from the signal from said oscillator, so as to produce in each arm of said cavity a microwave interrogating field interacting with the atomic beam atoms, the interrogating area being surrounded by a magnetic shielding.
Atomic beam resonators of this type are already known. The injection of the microwave energy is usually realized by a magnetic coupling by means of a T-H. In this case, the two microwave interrogating fields are in phase and the response of the resonator exhibits a maximum at the resonance frequency.
These known resonators exhibit important drawbacks from electrical and mechanical points of view. Thus, the coupling through a T-shaped waveguide element renders the resonator cumbersome. This coupling using a waveguide T which must cross the magnetic shielding produces important disturbances of the static magnetic field, which is unfavorable for obtaining good long term frequency stability and good accuracy. Moreover, owing to the fact that the response of the resonator has a maximum at the resonant frequency, the short term frequency stability of the resonator is limited by the shot noise associated with the atomic flux detected at the resonance. On the other hand, for this response of the resonator having a maximum at the resonant frequency, the amplitude of the frequency modulation applied to the interrogating signal must be relatively high, which causes important shiftings of the frequency of the atomic resonance in case for example of an untuning of the cavity.